The esperamicins are

chromoprotein A chromoprotein is a conjugated protein that contains a pigmented prosthetic group (or cofactor). A common example is haemoglobin, which contains a heme cofactor, which is the iron-containing molecule that makes oxygenated blood appear red. Other e ...

enediyne antitumor antibiotics of bacterial origin. Esperamicin A1 is the most well studied compound in this class. Esperamcin A1 and the related enediyne

calicheamicin The calicheamicins are a class of enediyne antitumor antibiotics derived from the bacterium ''Micromonospora echinospora'', with calicheamicin γ1 being the most notable. It was isolated originally in the mid-1980s from the chalky soil, or "calich ...

are the two most potent antitumor agents known. The esperamicins are extremely toxic DNA splicing compounds. Oxygen and active oxygen-radical scavengers have no significant influence upon DNA strand breakage by esperamicin, but the cleavage of DNA by esperamicin is greatly accelerated in the presence of thiol compounds. The preferential cutting sites of esperamicin are at thymidylate residues, and the frequency of nucleobase attacked (T greater than C greater than A greater than G) is different from that of calicheamicin (C much greater than T greater than A = G), neocarzinostatin (T greater than A greater than C greater than G), or bleomycin (C greater than T greater than A greater than G).Nucleotide-specific cleavage and minor-groove interaction of DNA with esperamicin antitumor antibiotics
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References

{{Enediynes Antibiotics Cancer research Enediynes Isopropyl compounds Carbamates Secondary alcohols Amines Phenol ethers Ethers Thioethers Alkene derivatives Anilides Benzoate esters Methyl esters Ketones Ten-membered rings